Tests for assert.epsilon failing on NaN

Tests to make sure assert.epsilon fails when either the epsilon or
actual arguments are NaN. Added a different failure message for the case
that epsilon is NaN.

Author: James Gibson

lib/assert/macros.js

@@ -17,7 +17,9 @@ for (var key in messages) {
 }
 
 assert.epsilon = function (eps, actual, expected, message) {
-    if (isNaN(actual) || Math.abs(actual - expected) > eps) {
+    if (isNaN(eps)) {
+        assert.fail(actual, expected, message || "cannot compare {actual} with {expected} \u00B1 NaN");
+    } else if (isNaN(actual) || Math.abs(actual - expected) > eps) {
         assert.fail(actual, expected, message || "expected {expected} \u00B1"+ eps +", but was {actual}");
     }
 };

test/assert-test.js

@@ -9,6 +9,12 @@ vows.describe('vows/assert').addBatch({
         },
         "`epsilon`": function() {
             assert.epsilon(1e-5, 0.1+0.2, 0.3);
+            assert.throws(function() {
+              assert.epsilon(1e-5, NaN, 0.3);
+            });
+            assert.throws(function() {
+              assert.epsilon(NaN, 1.0, 1.0);
+            });
         },
         "`match`": function () {
             assert.match("hello world", /^[a-z]+ [a-z]+$/);